client/cros/graphics: Introduce DRM-based screenshotting.

Directly take screenshots by mapping the framebuffers without using X11. This
effectively permits Freon-based screenshots during testing.

To test: Try to run something that uses screenshots. ui_SystemTray for
example. The test fails, but the screenshot succeeds.

BUG=chromium:412530
TEST=See above

Change-Id: If9160d3a2781f30be1edd0af5f9ce07ac115bd4a
Signed-off-by: Corbin Simpson <simpsoco@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/222973
Reviewed-by: Ilja Friedel <ihf@chromium.org>
2 files changed